Effect of Zn content on the microstructure and mechanical properties of A1MgSiCu alloys

AlMgSiCu alloys with different Zn contents were fabricated by conventional ingot metallurgy method. The effects of Zn content on the microstructures and mechanical properties of the alloys were investigated by optical microscopy, field emission scanning electron microscopy, tensile testing, and nanoindentation. It is found that Zn cun slightly refine the as-cast grain structure of the alloys. The grain boundaries become broader and more precipitates can form along the grain boundaries with the increase of Zn content; but the addition of Zn does not affect the phase components and morphology of the alloys. When the Zn content increases, the strength and elongation of the alloys increase firstly and then decrease. The alloy with the Zn mass fraction of 0.5% has the highest tensile strength, but the elongation of the alloy with the Zn mass fraction of 0.75% is the largest. Nanoindentation measurement shows that the elastic modulus decreases gradually with increasing Zn content.